This invention concerns an optical element for affecting the transmission characteristics through an optical system having at least two optical fiber end sections one of which is displaceable. The end sections can be optically coupled.
Such an element is for instance known from German Offenlegungsschrift 36 44 802. With such an element a switching function is realized by displacing optical fiber ends radially relative to one another so that light can travel from one fiber end section to the other fiber end section, while the light passage is blocked when the end sections are decoupled.
However, during switching, the known device needs to travel a considerable shifting distance, which practically corresponds to the thickness of the core of the optical fiber. This shifting distance already causes high switching times. In order to reduce the switching times, fast acting elements could be used. However, such elements require relatively high operating currents, are rather big and expensive. Such switches are therefore unsuited for constructing an optical fiber network.
An optical element for switching of optical power in optical fibers, which operates based on a different principle, has been known, for instance, from the book "Optische Telekommunikationssysteme, Band I; Physik und Technik", Publisher: W. Haist, Damm-Verlag KG, Gelsenkirchen-Buer. On pages 105 and 106 switchable light beam couplers are described, which operate with an integrated optical construction. With these couplers very short switching times are achievable. However, a coupling of optical fibers to the in- and output of planar structures is required, which causes, because of the different field distribution, high losses at the coupling regions.
Another disadvantage is that at the connection mechanical tolerances below 1 .mu.m have to be maintained. This Generates high manufacturing costs.
In addition, the planar wave guides themselves have comparatively high transition losses, so that transition losses of an optical switch lower than 3 dB would hardly be realizable.
Furthermore, with switching elements in integrated optical construction, the dependence on wavelength and polarization as well as the insufficient cross-talk attenuation, especially in local networks, is a disadvantage.
The present invention has therefore the object to create an optical element which can be affected in its transition function by an optical system of the aforementioned kind, which in respect to transition loss, non-pass attenuation, return loss, cross talk, switching time, manufacturing cost and/or size is an improvement over the existing optical elements and which is suited to be used in optical networks and therefore comes close to the requirement for an ideal switch.